Electrically heated appliances



March 19, 1957 TYLER 2,786,123

ELECTRICALLY HEATED APPLIANCES Filed June 29. 1954 2 Sheets-Sheet 1 FIG. I.

v Q 5 5 M o 9 5 A I. l 7' I 2 2 H a 4 2 I l 'y l7 27 I \v E g; V 1/ PUSH TO RESET 24 25 2 Sheets-Sheet 2 Filed June 29, 1954 FIG. 2.

IFPTUFHVEY ELECTRICALLY HEATED APPLIANCES Arthur Tyler, Staifordshire, England, assignor to Bulpitt and Sons Limited, Birmingham, England, a British com- P y Application June 29, 1954, Serial No. 440,033

Claims priority, application Great Britain July 4, 1953 7 Claims. (Cl. 219-20) This invention relates to electrical appliances incorporating an electrical resistance heating element such as kettles, coffee percolators, urns, water heaters, hot water storage tanks, washing boilers, washing machines, electric irons, and space heaters.

The term electrically-heated appliance as used in this specification, where the context so admits, is to be understood as including any of these and like electrically heated appliances.

The invention relates to such appliances in which the electrical heating circuit includes a thermally operative cut-out device for preventing over-heating of the heating element. The heating element is usually connected to the electric supply through a pin and socket coupling unit, the separable element of which is connected to the supply lead and the cut-out device comprises a spring-loaded plunger normally anchored to a fixed part by a fusible metal or by engagement with a bi-metallic strip. This rod is adapted to move the separable coupling element to separate the current carrying pin and socket connectors when the fusible metal softens and yields or the bi-met-allic strip deflects and disengages itself from the plunger.

Usually the ends of the heating element are connected to fixed pins and the separable coupling element is a socket connector. Hitherto the plunger has been arranged to eject the socket connector from the apparatus completely. This is inconvenient in apparatus which, for example, is provided with an outer casing or the socket connector is otherwise inaccessible. Furthermore by the ejection of the socket connector any earthing connection made through it is also broken. This may be dangerous in the event of the connecting lead, which is still live, having defective insulation which may allow live wires to come into contact with metallic parts of the body or casing of the apparatus.

The present invention consists in an electrically heated appliance incorporating an electrical resistance heating element and of the kind including a pin and socket coupling unit for the electric supply lead and a thermally operative cut-out device adapted upon over-heating of the element to release a spring-loaded plunger for moving the separable elements of the coupling unit to separate the pin and socket parts wherein the separable element is mechanically connected to the plunger and is retained in connection therewith even when the pin and socket parts are separated.

The mechanical connection of the separable coupling element to the plunger may be by frictional contact between them or the separable element may be positively but detachably anchored to the plunger.

The mechanical connection of the separable coupling element may be arranged to afford an electrically conductive path through which an earthing or grounding connection can be made even when the current carrying pin and socket parts are separated.

In electrically-heated appliances for liquid heating the thermally operative cut-out is mainly required to prevent over-heating of the resistance element in the absence of sufficient liquid to extract the heat being emitted but it nited States Patent may also be used with a thermostatically controlled heating element not only in liquid heating appliances but in other heating appliances such as electric irons and space heaters to safeguard the heating element in the event of failure of the thermostat.

So that the invention may be more clearly understood an embodiment will now be described in an immersion heater for a domestic washing machine.

Figure l is a plan view partly in section of the immersion heater and socket connector.

Figure 2 is a fragmentary plan view similar to Figure 1 showing the socket connector separated from current carrying connector pins of the immersion heater.

Figure 3 is a fragmentary cross-sectional view on line 33 of Figure 2.

The resistance wire 26 forming the heating element of the immersion heater 4 is enclosed in but insulated from a looped tubular casing 6 the ends of which are brazed or Welded to a mounting bracket 7 by which the immersion heater is mounted on the inside wall 8 of a container for heating liquids. The ends of lead wires 5 to the resistance wire 26 pass through bores in an insulating block 9 mounted in the bracket 7 to tubular connector pins 10 in the bores of which they are soldered or secured in some other suitable known manner. The pins form the fixed element of a coupling unit and the separable element is formed by a socket connector 11, sockets 12 of which engage the connector pins 10 and are wired to an electric supply lead 21.

Across the heating element casing of the immersion heater 4 is a straight tube 13 which encloses a plunger or red 14 urged by a spring 15 towards the coupling unit but normally held in the retracted position shown in Figure l with the spring 15 compressed by a fusible metal anchoring device 16 of well known construction. Extending axially from the end of the plunger 14 is a contact tongue 17 made of strip metal doubled over and both ends secured to the plunger 14. The contact tongue 17 is of rectangular cross-section, projects through a central opening in the block 9 and enters an axial recess 13 of complementary cross-section in the body of the socket connector 11. As shown in Figure 3 in an axial groove in one side of the body of the socket connector 11 is a resilient strip 19 which is anchored in the groove by a bearing strip 20 and screws 21. One end of the resilient strip 19 is doubled back to enter the recess 18 in which it comes into contact with the tongue 17. Between the other end of the resilient strip 19 and the bearing strip 20 is clamped an earthing or grounding conductor 22 of the supply lead 27. There is electrical continuity between the body of the container, the casing of the immersion heater and the plunger 14 so that by this means the apparatus can be earthed or grounded.

Axially extending from the end of the socket connector 11 opposite to the conductor pins 10 is a knob or spigot 23 of rectangular cross-section which is aligned with a complementary opening 24 in an outer casing 25 of the apparatus.

When overheating occurs the plunger 14 is released by the fusible metal device 16 and is urged by the spring 15 to push the socket connector 11 oif the connector pins 10 to break the current carrying circuit. The tongue 17 however remains in contact with the resilient strip 19 in the recess 18 so maintaining the earthing or grounding connection even though the current carrying pins and sockets are separated. In this separated or ejected position of the socket connector the knob or spigot 23 projects through the opening 24 and exposes to view a portion bearing instructions such as Push to reset. The current carrying pins and sockets are maintained in alignment for re-engagement by the co-operations of the rectangular cross-section plunger with the complementary cross-section of the recess 18 and of the rectangular 3 cross-section knob or spigot 23 with the cemplementarily shaped opening 24.

I claim:

1. An electrically heated appliance comprising an electrical resistance heating element, a pin and socket coupling unit adapted to connect the appliance to an electric supply lead and including a fixed coupling element and a separable coupling element having a recess, a plunger having a part received in the recess of the separable coupling element and in frictional engagement therewith in a manner resisting separation of the plunger from the recess, spring means for urging the plunger in the direction to separate the separable from the fixed coupling element, and a thermally operative device adapted to anchor the plunger in the spring-loaded position and upon reaching a pre-determined temperature to release the plunger and separate the separable from the fixed coupling element.

2. An electrically heated appliance comprising a conductive body, an electrical resistance heating element, a

pin and socket coupling unit adapted to connect the appliance to an electric supply lead and including a fixed and a separable element having a grounding contact connected to a grounding conductor of the supply lead, a plunger in electrical contact with the conductive body and in frictional and electrical contact with the grounding contact, spring means for urging the plunger in the direction to separate the separable from the fixed coupling element, and a thermally operative device adapted to anchor the plunger in the spring-loaded position and upon reaching a pre-determined temperature to release the plunger and separate the separable from the fixed coupling element, but to maintain contact between the plunger and the grounding conductor.

3. An electrically heated appliance according to claim 2 and including means for maintaining the current carrying pins and sockets of the coupling unit in alignment after separation in readiness for i e-engagement.

4. An electrically heated appliance according to claim 3 wherein the connection between the plunger and the separable coupling element maintains current carrying pins and sockets of the coupling unit in alignment for re-engagemeut.

5. An electrically heated appliance according to claim 2 and comprising a casing enclosing the coupling unit and having an opening therethrough, the separable coupling element having an axially extending knob aligned "i with the opening and projecting through it when the separable and fixed coupling elements are separated.

6. An electrically heated appliance comprising an electrical resistance heating element, a pin and socket coupling unit adapted to connect the appliance to an electric supply lead and including a fixed and a separable element, a plunger mechanically coupled to the separable coupling element, spring means for urging the plunger in the direction to separate the separable from the fixed coupling element, a thermally operative device adapted to anchor the plunger in the spring-loaded position and upon reaching a pre-determined temperature to release the plunger and separate the separable from the fixed coupling element and a casing enclosing the coupling unit and having a non-circular opening therethrough, the separable coupling element having an axially extending knob ot' a cross-section of a shape complementing said opening of said casing, said knob being aligned with said opening and projecting through it when the separable and fixed coupling elements are separated, the engagement of the knob with the opening retaining the pins and sockets in alignment in the ejected position.

7. An electrically heated appliance with a metallic body, comprising in combination an electric heater, an inlet socket having contact pins connected to the heater, and an inlet plug having current-carrying contact sockets and a grounding contact and adapted to be wired to a supply lead including a grounding conductor, a plunger retentively coupled to the inlet plug and in electrical continuity with the metallic body and with the grounding contact, spring means for urging the plunger in the direction to separate the inlet plug from the inlet socket, and a thermal cut out adapted to anchor the plunger in the spring-loaded position and upon reaching a pre-determined temperature to release the plunger and separate the inlet socket but to maintain contact between the plunger and the grounding conductor.

References Cited in the file of this patent UNITED STATES PATENTS 937,332 Richardson Oct. 19, 1909 1,015,954 Hadaway Jan. 30, 1912 1,039,810 Rose Oct. 1, 1912 2,171,866 Rowe Sept. 5, 1939 2,172,495 Bulpitt Sept. 12, 1939 2,286,340 Bulpitt June 16, 1942 

